As to production of negative photoresist patterns, JP2014-115631A proposes a photoresist composition containing a resin which has not structural unit having an acid-labile group but a structural unit represented by formula (I) and a structural unit represented by formula (a4), a resin which has a structural unit represented by formula (II) and a structural unit having an acid-labile group, and an acid generator.

(In the formulae, R2 represents a C3 to C18 alicyclic hydrocarbon group, R4 represents a C1 to C20 saturated hydrocarbon group having a fluorine atom, A21 represents a single bond or the like.)